Show understanding of how an OS can maximise the use of resources

What is an OS? 🖥️

An OS is the software that sits between the computer hardware and the applications you use. It manages the computer’s resources so that all programs can run smoothly.

Key Purposes of an OS

• Resource Management – CPU, RAM, storage, and I/O devices.
• Process Management – launching, scheduling, and terminating programs.
• Memory Management – allocating and protecting memory.
• Storage Management – organising files and directories.
• Security & Protection – user authentication and access control.
• User Interface – command line or graphical interface.

Resource Management Analogy

Think of the OS as a traffic controller at a busy intersection. It directs cars (processes) so they don’t crash (conflict) and ensures everyone reaches their destination (uses resources) efficiently.

Process Management in Detail

The OS keeps a list of all running processes, assigns CPU time using scheduling algorithms (e.g., Round Robin, Priority), and handles inter‑process communication.

1. Creation – fork() or spawn()
2. Execution – CPU allocation
3. Termination – clean up resources

Memory Management Techniques

The OS uses paging and segmentation to divide memory into blocks. It also employs virtual memory to make a small physical RAM appear larger.

Example: If a program needs 8 MB but only 4 MB is free, the OS swaps out part of another program to disk.

Storage Management

Files are organised in a hierarchical file system (folders & sub‑folders). The OS handles file permissions, directory structures, and file allocation.

Security & Protection

The OS authenticates users, enforces access rights, and isolates processes to prevent one program from corrupting another.

User Interface

The OS can provide a command line interface (CLI) or a graphical user interface (GUI) to make interaction easier.

Maximising Resource Use

The OS aims to keep the CPU, memory, and I/O devices busy but not overloaded.

• CPU utilisation: Scheduling ensures every process gets a fair share.
• Memory utilisation: Paging and segmentation reduce fragmentation.
• I/O optimisation: Buffering and caching speed up read/write operations.

Exam Tips for 16.1

• Define each OS purpose clearly.
• Use the traffic controller analogy to explain resource allocation.
• Show how paging and virtual memory help maximise RAM usage.
• Remember the four key OS roles (CPU, memory, storage, I/O).
• Include a short table summarising OS functions – examiners love concise tables.